Additive Manufacturing (AM), commonly known as 3D printing is a production method that utilises repeated addition of layers in order to produce a final shape. AM utilises less raw material and does not have drawbacks such as tool wear and material wastage as seen in conventional machining. However, they do have drawbacks such as poor surface and internal defects.  A common practice in AM is the fabrication of contour and bulk region using separate parameters.  The aim of this project was to study the effects of various process parameters on the contour properties. The process parameters considered were scanning speed, beam current and focus offset. The Nickel alloy Inconel 718 was utilised in Electron Beam Melting (EBM) to fabricate the test specimen. The samples used in this project were in an as-built condition which was priorly subjected to tensile testing for a different project. The tests performed in this project are hardness testing and microstructural investigation about grains, precipitates and the various defects.  The test results helped to understand the effect of various process parameters on the hardness and microstructure of the samples. The samples with lower scanning speed had higher hardness and lesser lack of fusion than samples with higher speed. In the case of varying beam current, the samples with higher beam current had higher hardness values and fewer lack of fusions. Similarly, the effects of varying two or more process parameters were also studied and their findings recorded. The microstructure consisted of a large number of shrinkage porosities in the bulk and contour regions. The presence of Niobium rich precipitates at grain boundaries and the grain structure for various process parameters were identified and recorded.

A new model of the material flow in rotary friction welding of tubes is proposed. The material flow proposed is based on 3D scans of welds performed with tungsten tracers. The tracers indicate a bifurcation of flow into two deformation paths. A different analysis is performed on each path.The material in Path 1 interacts with the weld interface and exhibits large amounts of azimuthal flow. Previous analytical investigations that have analytically modelled the weld interface as a non-Newtonian fluid are used to calculate the strain rate in this zone.The material in Path 2 transitions from axial to primarily radial flow. The assumption of no azimuthal flow in Path 2 is validated through experimental results of the tracer study. The directional transition in this path is compared to orthogonal machining and equal channel angular pressing. The process to estimate the variables needed to calculate strain and strain rates using the equations from orthogonal machining and equal channel angular pressing is defined. Strain and strain rate in Path 2 are dependent upon feedrate and upset. Both decrease throughout the welding process. The strain rate is higher than previous studies in rotary friction welding because of the deformation model proposed.

Finite element models of friction welding can be used to estimate internal conditions of welds which are useful for weld analysis and developing experimental welding procedures. Many modeling techniques are used to accomplish these goals, each with relative strengths and weaknesses. A comparative analysis of friction welding models using different heat generation methods is presented. The three different heat generation methods examined were viscoplastic friction, constant steady-state generation, and experimentally measured power data. The models were compared against each other using three output measurements: temperature, axial force, and upset. The friction model predicted temperatures within 40 degrees C. Temperature accuracy improved at a higher upset rate and higher spindle speed, when weld samples heated up faster. The model was excellent at predicting upset, with accuracy within 1.5%. Maximum force was predicted within 9-18%. The constant heat generation model typically predicted temperatures within 30 degrees C. Upset was estimated within 7%. Maximum force was predicted within 12% at high feed rates, but accuracy dropped to 28% when feed rate was reduced. The motor power model was the most accurate model at estimating temperature, with a typical accuracy within 25 degrees C. Axial upset was predicted within 5%. Maximum force was predicted within 1-8%, with greater accuracy occurring at higher feed rates.

The research is focused on cladding of inconel 625 using the MAG - CMT method. It was found that welding without an oscillation does not create the necessary geometry to establish additional layers. When welding with an oscillation, it was researched that the current between 150 and 200 A appears most appropriate in the synergistic mode for welding inconel 625. The resulting weld bead was made at a current of 190 A with pulse dynamics correction set to -4 and correction of arc length to +10 and welding speed of 315 mm per minute.The weld bead was not ideal mainly due to insufficient height. The improvement of results could be achieved by set oscilation with fluent change in acceleration. Because of the time options and difficulty of programming it was used only constant speed for all experiments.

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High Power Impulse Magnetron Sputtering (HiPIMS) comes as a new and promising PVD method for the development of high-performance coatings for cutting applications. This technique utilizes high energy and ionization which can produce a denser and stronger ceramic in comparison to traditional deposition techniques. Important coating characteristics that arise from this method such as enhanced hardness, adhesion, and less defects, can be applied when machining hard-to-cut materials. In this study, investigation of tool life and wear mechanisms, mechanical and physical properties of AlTiN coatings deposited on carbide tools by HiPIMS and Cathodic Arc Evaporation (CAE) were analyzed when machining Inconel 718 and Stainless Steel 304. Experimental turning tests were performed to evaluate tool life, and the wear mechanisms were analyzed by optical and scanning electron microscopy. Nanohardness, scratch test, fracture toughness and other methods were carried out to evaluate the coating properties. Impedance experiments were performed to determine the coating porosity and resistance to corrosion. The results showed that HiPIMS coating presented higher hardness, toughness to fracture and adhesion to the substrate in comparison to CAE coatings. The HiPIMS coated tool substantially improved tool life when machining Inconel. The dominant wear mechanism found was abrasion, which is induced by the presence of hard carbides. The main wear patterns observed were flank, notch, and crater wear. The tool performance of HiPIMS was found to have enhanced mechanical properties, lower porosity, and form a larger amount of tribo-oxides when machining, in comparison to CAE. / Thesis / Master of Applied Science (MASc)

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